uniapp 图片文件流

uni.request({
  url: '*****', //仅为示例，并非真实接口地址。
  method: 'GET',
  responseType: 'arraybuffer',
  data: {
},
  header: {
    'content-type': 'application/json',
    'token': 'token'
  },
  success: (res) => {
    // 返回的是文件流
    let datas = res.data
    let blob = new Blob([ datas], {
      type: 'application/pdf;charset=UTF-8'
    })
    let pdfData = window.URL.createObjectURL(blob) //创建预览路径
    let agreementUrl = encodeURIComponent(pdfData)

   let codeImg = 'data:image/png;base64,' + btoa(
        new Uint8Array(datas).reduce((datas, byte) => datas + String.fromCharCode(byte), '')
    );

  }
});